← Back to dex
Common exoplanet 21 EP

K2-173 b

RA 60.3752° · Dec 15.6251° · exoplanet

Loading sky survey…
🌌 View in 3D star map
Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 3 badges
21 pts · Common
Common 22 pts → Uncommon
  • Super-Earth +8
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
Total score 21

1 more point to reach Uncommon.

Badges

  • Confirmed exoplanet · +5
  • Super-Earth · +8
  • Orbits a Sun-like star · +8

Trivia

What it actually is

  • Hugging its star. It orbits closer to its star than Mercury does to the Sun, completing a lap in less time than Mercury takes.
  • What it is made of. Its density says rock, though lighter than Earth's mix: probably less iron, or a thick shell of water and ice over the top.

Sense of scale

  • In perspective. Far away by human standards, yet still a local address inside the Milky Way's spiral arms.

Find it in the sky

  • How to spot it. At magnitude 12.5 it is far too faint for the eye: this one belongs to cameras and long exposures.
  • Northern sky. It rides the northern half of the sky — an easier target the further north you are.
  • Best time of year. It stands highest in the middle of the night around November — that's when to go looking.

Could we get there?

  • Verdict. Hopelessly far for any craft humanity can build today.

Getting there

  • Aboard Voyager 1. ≈ 13.1 million years at Voyager 1's speed (17 km/s).

Properties

density gcc
4.25
diameter km
20515.311
discovery facility
K2
discovery method
Transit
discovery year
2018
dist ly
745.7263
host star teff
5580
inclination
87.8256
mag
12.523
mass earth
3.22
name
K2-173 b
orbital period days
5.8687
radius earth
1.6083
sys num planets
1
sys num stars
1

About K2-173 b

K2-173 b is a common exoplanet. It lies about 745.7 light-years from Earth, shines at apparent magnitude 12.52, spans roughly 1.61 Earth radii and weighs about 3.22 Earth masses.

It orbits closer to its star than Mercury does to the Sun, completing a lap in less time than Mercury takes.

How to see it

At apparent magnitude 12.52, it takes a larger telescope or a long-exposure image to capture.

Like any astronomical target, K2-173 b is best seen from a dark site away from city lights, and when it is above the horizon depends on your latitude and the time of year. The visibility panel above works out tonight's viewing window for your saved location.

Why K2-173 b is a common exoplanet

K2-173 b scores 21 points on Spacedle's rarity scale, which places it in the common tier. Another 1 point would lift it into a rarer tier.

That score comes from 3 science badges — Confirmed exoplanet, Super-Earth and Orbits a Sun-like star — each earned for a real, measurable property of the object. Rarity on Spacedle is never random: the more remarkable an object's astrophysics, the more badges it collects, the higher it scores, and the rarer it ranks.